I have a 98 civic with 270k km and every couple of weeks the engine light comes on. I finally got a code reader and I get the po420. Powertrain Catalyst system low efficiency and system below threshold bank1.

Can anyone help me with this. Thanks.

 

it looks to me like your cat is going out; download the 96-98 factory service manual and verify that code P0420 is indicative of that. It should give you some diagnostics.

 

I'm assuming cat means catalytic converter. I have a chilton book so I will check it first as I am on dialup and it will take a few hours to download the service manual.

 

yes, double check that the code implies a malfunctioning cat.

 

OK... Catalyst efficiency code. Its not necissarily the Cat going bad. It just means that the ECU isnt seeing the right ammount of variation in the up and down stream o2 sensors. Part of the diagnostics on that one is A) make sure there are no vacuum leaks, B) You either need an advanced scanner or Lab Scope to compare the up and down stream sensor readings. Since I dont have my ALLData on the home PC here, I cant spit out all the Diag. for that code, but thats a good start from memory.

It could be as simple as one of your o2 sensors going bad. Codes are never a "fix-all" . All they do is give you a place to start looking.

 

I am using the ProScan 5 software and I think this will allow me to compare the information between the o2 sensors. This software runs on my laptop and I have an OBD reader that plugs in. I will research how to use the software and hopefully get to the bottom of this problem. Is this a big problem or can I just keep resetting the error code?

Thanks for your help.